The invention relates to a method for correcting measured values of a coordinate measuring machine and a corresponding machine, and more particularly to a method for correcting measured values taking into account mechanical deformations occurring in the measurement process.
Coordinate measuring machines are often used to analyze the surface of workpieces. Systematic measurement errors may occur because elements and components of the coordinate measuring machine bend during the measurement operation. Mention is to be made here primarily of the bending of the probe head, in particular the probe pin, but also the bending of structural components of the coordinate measuring machine. Such bendings in the region of the probe head and the probe pin are essentially a result of the applied contact or measurement force. However, forces which occur when the moving elements of the coordinate measuring machine are accelerated or decelerated, in connection with their masses, may also play a role.
Bending of a coordinate measuring machine element involved in the measurement operation naturally leads to measurement errors. Attempts have therefore been made in a wide variety of ways to compensate for such measurement errors using correction methods.
It is known from DE 101 24 493 A1 to determine the dynamic bending behavior of a probe as a parameter field, in particular as a tensor, in order to calculate correction values from this parameter field while taking into account the acceleration acting on the probe, and finally to correct the measurement results of the probe using the correction values.
In coordinate measuring machines, it is furthermore known to calibrate the position of the probe sphere arranged on the free end of the probe tip of the probe head in space with the aid of so-called calibrating bodies. Conventionally, these calibrating bodies are configured as spheres which are arranged in the measurement region of the coordinate measuring machine and which can be approached by the probe sphere at almost any desired angles. In the scope of the present invention, the calibrating body is considered to be an element of the coordinate measuring machine.
It is known from DE 198 09 589 A1 to approach a calibrating body, in particular a calibrating sphere, with the probe head and guide the probe sphere along a path on the surface of the calibrating body, which is not restricted to a plane. The calibrating data assigned to the probe are calculated from the measured values recorded in this way.
Another disadvantage of known methods is that errors may also occur owing to the flexibility of the workpiece to be analyzed.